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Every year, it seems I am on a training ride 5-10 miles from home and while torquing up, I snap the hanger throwing the rear derailleur into my spokes and locking up my rear wheel. I am 205lbs and 5'10" and still squat pretty heavy so I am wondering if the combination of my weight and my force is wearing out the hangers quickly causing this and if there is a known way to check this for fatigue before I get on the road. I use a 2012 GTR Series 5 aluminum bike. If I ask at a bike shop, they will just try and sell me a tri bike. I want a tri bike but I don't want one if it wont change anything in my sprint and olympic tri experience.

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    It sounds like you've got something misadjusted -- too short chain, the derailleur hangers not being put on properly, etc. Try a different bike shop. – Batman Apr 6 '15 at 23:35
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    If you use the bike properly, additional force on the pedals has no effect on the force on the derailer hanger. You basically have a problem with the derailer -- either it's misadjusted or you're being far too forceful in your shifting, and not letting the indexed shifter do its thing. Also, you should get a spoke guard for the bike, so a the derailer does not jamb the spokes when it goes too far inward. – Daniel R Hicks Apr 7 '15 at 1:36
  • (You might want to have a cyclist friend check out your shifting technique.) – Daniel R Hicks Apr 7 '15 at 1:37
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    Don't shift under full load. Ease off on pedaling when shifting. – Dissenter Apr 7 '15 at 5:08
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    There is also the possibility that you are pedaling hard enough to cause the wheel's axle to shift forward and twist, which could cause various problems. You may simply need to set the quick release tighter, or you may need a "wheel tug" to hold it in place. – Daniel R Hicks Apr 7 '15 at 11:34
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The way you asked the question, it sounds like you think the following is happening: first, the derailleur hanger wears out/weakens, then it snaps, and this causes the derailleur to go into the spokes.

It is much more likely that the chain of events is the following: the derailleur is mis-adjusted, when you shift to the largest cog on the rear, the derailleur goes into the spokes, and this causes the derailleur hanger to break off.

Possible causes:

  1. the inner limit screw on the rear derailleur is too far out, needs to be tightened a bit, until it reliably keeps the derailleur from moving too close to the spokes

  2. the chain is too short, and when you shift onto the largest rear cog and the largest front chainring (not recommended in general), the chain gets too tight and this rips off the derailleur.

  • In addition to what you have said, it is possible that while our B O B puts the force in the pedals other parts of the bicycle start to flex, like rear triangle and wheel, especially if this is done out of the saddle. This flex could eat up already small clearance of miss adjusted derailleur, and throw it in the spokes and causing sequence of events you have described. – Davorin Ruševljan Nov 17 '15 at 10:19
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I had this exact experience the first time I tried going up a significant slope. The bike was fine all the way on the flat, but as soon as the grade increased I was putting a lot more force into the transmission.

I heard the spokes going "tink, tink-tink, tink" as the edge of the deraillereur tapped the spokes. That was the warning that I did not recognise.

At the steepest bit, I pushed really hard in bottom gear, and the cage of the bottom jockey wheel caught a spoke, and wrapped itself up towards the brake.

After going home, the fix was to put a beefier hanger and derailuer in place, and it did not flex under load as much as the old tinny hanger.

Summary: Hearing tinking noises is a warning, don't ignore it.

  • But what caused the problem is the first place? There is no reason why the hanger would be under more load on a hill (unless the chain is too short). – Daniel R Hicks Nov 17 '15 at 1:36
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    Yes, this experience report is about derailleur adjustment. The hanger is just collateral damage. – andy256 Nov 17 '15 at 2:07

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